Cerebral Edema, Hydrocephalus & Raised Intracranial Pressure & Herniation Flashcards
The brain and spinal cord are protected by the rigid compartment defined by the __________, ________,and ____________
skull, vertebral
bodies, and dura mater.
Generalized brain edema, increased CSF volume (hydrocephalus),
and focally expanding mass lesionsmayincrease ____________. Depending on the
degree and rapidity of this increase and the nature of the underlying lesion, the consequences
range from subtle neurologic deficits to death.
intracranial pressure
Cerebral edema or, more precisely, brain parenchymal edema, is of two principal types:
- Vasogenic edema
- Cytotoxic edema
Vasogenic edema is caused by __________ and ____________, allowing fluid to shift from the intravascular compartment to the intercellular
spaces of the brain.
- blood-brain barrier disruption and
- increased vascular permeability
The paucity of_________greatly impairs the resorption of excess
extracellular fluid.
lymphatics
Walang lymphatics okay?
Vasogenic edema may be either___________ or ____________
- localized (e.g., adjacent to inflammation or neoplasms) or
- generalized
What is Cytotoxic edema ?
It is an** increase in intracellular fluid** secondary to neuronal, glial, or
endothelial cell membrane injury, as might be encountered in someone with a
generalized hypoxic/ischemic insult or with metabolic damage.
In practice, conditions associated with _________ often have elements of both
vasogenic and cytotoxic edema.
generalized edema
____________ occurs especially around the lateral ventricles when
an increase in intravascular pressure causes an abnormal flow of fluid from the intraventricular
CSF across the ependymal lining to the periventricular white matter.
Interstitial edema (hydrocephalic edema)
In generalized edema, the
gyri gross appearance are___________.
As the brain expands, herniation may occur.
flattened, the intervening sulci are narrowed, and the ventricular cavities are
compressed
The __________ within the ventricular system produces CSF, which normally circulates
through the ventricular systemandenters the cisterna magna at the base of the brain stem
through the foramina of LuschkaandMagendie.
choroid plexus
Subarachnoid CSF bathes the superior
cerebral convexities and is absorbed by the arachnoid granulations.________ refers to
the accumulation of excessive CSF within the ventricular system ( Fig. 28-2 ).
Hydrocephalus
In hydrocephalus the most cases occur
as a consequence of_____________-;
impaired flow and resorption of CSF
only rarely is overproduction the
cause of hydrocephalus (e.g., with ________________).
tumors of the choroid plexus
When hydrocephalus develops in infancy before closure of the cranial sutures, there is
________________, manifested by an increase in head circumference.
enlargement of the head
Hydrocephalus
developing after infancy when sutures are closed in contrast, is associated with___________________, without a change in head circumference.
** expansion of the ventricles and
increased intracranial pressure**
** If only a portion** of the
ventricular system is enlarged because of excess CSF, as may occur because of a mass in the
third ventricle, the pattern is called_______________
noncommunicating hydrocephalus.
In______________ there is enlargement of the entire ventricular system.
communicating hydrocephalus
So what is the difference between communicating and noncommunicating hydrocephalus?
Communicating = ENTIRE
Noncommunicating= A part only
The term hydrocephalus
ex vacuo refers to _______________________
dilation of the ventricular system with a compensatory increase in CSF
volume secondary to a loss of brain parenchyma.
When the volume of the brain increases beyond the limit permitted by compression of veins and
displacement of CSF, the pressure within the skull will increase.
Most cases are associated with
a _________________
.
mass effect, either diffuse, as in generalized brain edema, or focal, as with tumors,
abscesses, or hemorrhages
Elevated intracranial pressure may also reduce perfusion of the
brain, further exacerbating cerebral edema. Because the cranial vault is divided by ____________, localized expansion of the brain may cause it to be displaced in
relation to these partitions. If the expansion is sufficiently severe, a herniation syndrome may
occur
rigid dural
folds (the falx and tentorium)
Subfalcine (cingulate) herniation occurs when _____________ of a
cerebral hemisphere displaces the cingulate gyrus under the falx cerebri. This may lead
to compression of branches of the anterior cerebral artery.
unilateral or asymmetric expansion
Transtentorial (uncinate, mesial temporal) herniation occurs when the_______________.
medial aspect of
the temporal lobe is compressed against the free margin of the tentorium
With
increasing displacement of the temporal lobe, the third cranial nerve is compromised,
resulting in________________.
pupillary dilation and impairment of ocular movements on the side of the
lesion
The posterior cerebral artery may also be compressed, resulting in______________
ischemic
injury to the territory supplied by that vessel, including the primary visual cortex.
When
the extent of herniation is large enough the contralateral cerebral peduncle may be
compressed, resulting in hemiparesis ipsilateral to the side of the herniation; the change
in the peduncle in this setting is known as _____________
Kernohan’s notch.
Progression of
transtentorial herniation is often accompanied by hemorrhagic lesions in the midbrain
and pons, termed _____________( Fig. 28-4 ).
secondary brainstem, or Duret, hemorrhages
Describe the Duret, hemorrhages
These
linear or flame-shaped lesions usually occur in the midline and paramedian regions and
are believed to be due to distortion or tearing of penetrating veins and arteries
supplying the upper brainstem.
Tonsillar herniation refers to ___________. This pattern of herniation is life-threatening because it causes brainstem
compression and compromises vital respiratory and cardiac centers in the medulla
oblongata.
displacement of the cerebellar tonsils through the foramen
magnum
